A low stress cryogenic mount for space-borne lithium fluoride optics

E. Todd Kvamme; Dario Trevias; RaShelle Simonson; Larry Sokolsky

doi:10.1117/12.613453

30 August 2005 A low stress cryogenic mount for space-borne lithium fluoride optics

E. Todd Kvamme, Dario Trevias, RaShelle Simonson, Larry Sokolsky

Proceedings Volume 5877, Optomechanics 2005; 58770T (2005) https://doi.org/10.1117/12.613453
Event: Optics and Photonics 2005, 2005, San Diego, California, United States

Abstract

Single crystal Lithium Fluoride has been base-lined as one of the optical materials for the Near Infra-Red Camera (NIRCam) on the James Webb Space Telescope (JWST). Optically, this material is outstanding for use in the near IR. Unfortunately, this material has poor mechanical properties, which make it very difficult for use in any appreciable size on cryogenic space based instruments. In addition to a dL/L from 300K to 30K of ~-0.48%, and a room temperature CTE of ~37ppm/K, the material deforms plastically under relatively small tensile loading. This paper will present a mount that has been proven via vibration and thermal-vacuum testing to successfully mount a large (70mm-94mm) Lithium Fluoride optic for application in space. An overview of Lithium Fluoride material properties and characteristics is given. A design limit load is determined for the material based on strength values from the literature as well as independent testing. The original design option is shown and the pros and cons discussed. The final mount design is then presented along with analysis results showing compliance to the limit load requirement. Finally, testing results are discussed showing survival of the optic in a space launch vibration environment as well as survival during cool-down to the operational thermal environment of 30K.

Citation Download Citation

E. Todd Kvamme, Dario Trevias, RaShelle Simonson, and Larry Sokolsky "A low stress cryogenic mount for space-borne lithium fluoride optics", Proc. SPIE 5877, Optomechanics 2005, 58770T (30 August 2005); https://doi.org/10.1117/12.613453

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